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kernel: trace: preemptirq_delay_test: add cpu affinity

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The kernel thread executing test can run on any cpu, which might be
different cpu latency tracer is running on, as a result, the
big latency caused by preemptirq delay test can't be detected.

Therefore, the argument cpu_affinity is added to be passed to test,
ensure it's running on the same cpu with latency tracer.

e.g.
cyclictest -p 90 -m -c 0 -i 1000 -a 3
modprobe preemptirq_delay_test test_mode=preempt delay=500 \
burst_size=3 cpu_affinity=3

Link: https://lkml.kernel.org/r/1611797713-20965-1-git-send-email-chensong_2000@189.cn

Signed-off-by: Song Chen <chensong_2000@189.cn>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Song Chen 2021-01-28 09:35:13 +08:00 committed by Steven Rostedt (VMware)
parent befe6d9465
commit 4b9091e1c1
2 changed files with 18 additions and 0 deletions
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4
kernel/trace/Kconfig
View File

@ -886,6 +886,10 @@ config PREEMPTIRQ_DELAY_TEST
irq-disabled critical sections for 500us:
modprobe preemptirq_delay_test test_mode=irq delay=500 burst_size=3
What's more, if you want to attach the test on the cpu which the latency
tracer is running on, specify cpu_affinity=cpu_num at the end of the
command.
If unsure, say N
config SYNTH_EVENT_GEN_TEST

14
kernel/trace/preemptirq_delay_test.c
View File

@ -21,13 +21,16 @@
static ulong delay = 100;
static char test_mode[12] = "irq";
static uint burst_size = 1;
static int cpu_affinity = -1;
module_param_named(delay, delay, ulong, 0444);
module_param_string(test_mode, test_mode, 12, 0444);
module_param_named(burst_size, burst_size, uint, 0444);
module_param_named(cpu_affinity, cpu_affinity, int, 0444);
MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)");
MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)");
MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)");
MODULE_PARM_DESC(cpu_affinity, "Cpu num test is running on");
static struct completion done;
@ -36,7 +39,9 @@ static struct completion done;
static void busy_wait(ulong time)
{
u64 start, end;
start = trace_clock_local();
do {
end = trace_clock_local();
if (kthread_should_stop())
@ -47,6 +52,7 @@ static void busy_wait(ulong time)
static __always_inline void irqoff_test(void)
{
unsigned long flags;
local_irq_save(flags);
busy_wait(delay);
local_irq_restore(flags);
@ -113,6 +119,14 @@ static int preemptirq_delay_run(void *data)
{
int i;
int s = MIN(burst_size, NR_TEST_FUNCS);
struct cpumask cpu_mask;
if (cpu_affinity > -1) {
cpumask_clear(&cpu_mask);
cpumask_set_cpu(cpu_affinity, &cpu_mask);
if (set_cpus_allowed_ptr(current, &cpu_mask))
pr_err("cpu_affinity:%d, failed\n", cpu_affinity);
}
for (i = 0; i < s; i++)
(testfuncs[i])(i);